1. Field of the Invention
This invention relates generally to a fender forming system, and specifically to a method and apparatus for forming a curve in a substantially planar portion of a fender blank.
2. Description of the Prior Art
The fenders for tandem wheel trailers, such as truck trailers, horse trailers, and boat trailers, have a curved portion on each end and a straight portion in the middle. These fenders have been made in the prior art by first cutting a substantially planar plate to shape with a dye cut machine. In the industry, this plate is referred to as a "fender blank." Normally, a flange will be formed on one or more edges of the fender blank by a press. Then, each end of the fender blank is rolled through a rolling machine to form the curved portion on each end.
The prior art roller machines have a pair of driven pinch rollers that are spaced to receive the workpiece between them. Guide rollers are located on the front and back of the pinch rollers. The guide rollers are positioned to cause the workpiece to bend as it passes through the pinch rollers. This results in the curve.
The prior art roller machines "rolled" the workpiece by simultaneously forcing the workpiece through the pinch rollers and bending the workpiece. The prior art systems often require multiple passes of the workpiece through the rollers to achieve the desired degree of curvature. These systems are manually operated, and consequently subject to human error, waste of materials, inaccuracy, defective or substandard fenders, and inconsistency. Moreover, this process is labor intensive, requiring extensive training, and resulting in considerable manufacturing expense.
A number of significant manufacturing problems and product defects were encountered in the prior art including scuffs, bows, crimps, and knots. Scuffing results when the pinch rollers worked against the fender blank to abrade the outer surface, detracting from the appearance of the fender. Bows also occur in the use of pinch rollers, and are characterized by undesired curvature in the width of the fender blank. Crimps are common manufacturing errors, characterized by a wrinkle or gathering of a portion of the fender usually at or near the flange formed along the edge of the fender. Knots are also common in the prior art systems, and are characterized by a distortion in the material at the transition of the planar portion of the fender to the curved portion of the fender.